US9275656B1 - Disk drive with channel and preamp with dynamic write-current control for write head - Google Patents
Disk drive with channel and preamp with dynamic write-current control for write head Download PDFInfo
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- US9275656B1 US9275656B1 US14/804,063 US201514804063A US9275656B1 US 9275656 B1 US9275656 B1 US 9275656B1 US 201514804063 A US201514804063 A US 201514804063A US 9275656 B1 US9275656 B1 US 9275656B1
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- 230000007704 transition Effects 0.000 claims abstract description 56
- 239000000872 buffer Substances 0.000 claims description 12
- 230000001939 inductive effect Effects 0.000 claims description 7
- 239000000696 magnetic material Substances 0.000 claims description 6
- 239000010409 thin film Substances 0.000 claims description 5
- 239000002131 composite material Substances 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 2
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- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000013500 data storage Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
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- 238000007493 shaping process Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
- G11B5/55—Track change, selection or acquisition by displacement of the head
- G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
- G11B5/5526—Control therefor; circuits, track configurations or relative disposition of servo-information transducers and servo-information tracks for control thereof
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
- G11B5/09—Digital recording
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/10009—Improvement or modification of read or write signals
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/10009—Improvement or modification of read or write signals
- G11B20/10018—Improvement or modification of read or write signals analog processing for digital recording or reproduction
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/10009—Improvement or modification of read or write signals
- G11B20/10305—Improvement or modification of read or write signals signal quality assessment
- G11B20/10388—Improvement or modification of read or write signals signal quality assessment control of the read or write heads, e.g. tracking errors, defocus or tilt compensation
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
Definitions
- Embodiments of the invention relate generally to methods and devices used in magnetic data storage systems with rotating disks, and more particularly to generation of signals for driving inductive write heads, which are used in such systems.
- a prior art disk drive 10 typically includes a main integrated circuit, which is typically called a system on a chip (SOC) 11 that contains many of the electronics and firmware for the drive including the read/write channel system 31 .
- SOC system on a chip
- Each disk can have thin film magnetic material on each of the planar surfaces.
- Each disk surface normally has a dedicated pair of read and write heads packaged in a slider 13 that also includes fly-height control components.
- the sliders are mechanically mounted on an actuator (not shown) with various flexible components to allow appropriate degrees of movement during operation.
- Each slider is a sub-component of a head gimbal assembly (HGA) that typically includes a suspension assembly with a laminated flexure with copper traces to carry the electrical signals to and from the heads.
- the read and write heads (sensors) heads and associated connections are conventionally formed using thin film lithographic patterning in which a series of thin films deposited and patterned on the trailing surface slider.
- the sliders are selectively positioned over tracks on the rotating disk by the actuator (not shown).
- the actuator also supports the electrical connections to the slider components and contain the arm electronics (AE) chip 12 which typically include preamplifiers (preamps) for the read heads, write drivers and fly-height controls.
- AE arm electronics
- a flex cable (not shown) connects the SOC 11 to the AE 12 .
- the AE typically include digital and analog circuitry that control the signals sent to components in the slider and processes the signals received from the slider components.
- the write driver preamp 18 generates an analog current signal that is applied to the inductive coil in the write head 15 to write data by selectively magnetizing portions of the magnetic material on the surface of the rotating disk and creating magnetic transitions. An adjacent pair of magnetic transitions is generally called a dibit.
- CML Current-mode logic
- I/O digital input/output
- CML is a differential logic family that is used to transmit serial data to the write driver preamp to produce the pre-programmed wave shape at the write driver's output.
- the write driver's signal is then applied to the write transducer that writes the data to the disk media.
- the control of the shape and amplitude of the current signal that is applied to the inductive coil in the write head 15 by the write driver preamp 18 is critical for optimizing the recording performance.
- Conventionally disk drives use write current overshoot amplitude (OSA) control to ensure that the write current reaches a peak value before the next magnetic transition.
- OSA write current overshoot amplitude
- Write pre-compensation circuits are also used to compensate for non-linear bit shift caused by closely spaced transitions.
- An efficient magnetic field is particularly important when writing a relatively long magnetic section (called a long magnet) on a data track.
- a long magnet is an area of a track that is magnetized in one direction with a relatively long spacing between transitions.
- FIG. 2 illustrates the adjacent tracks erasure problem for repeatedly written tracks on disk 20 .
- the adjacent tracks next to the track where write head pole 21 is positioned are subject to erasure from the field that extends beyond the width of the target track.
- the shields in the slider can also cause stray magnetic fields which place nearby tracks at risk of being inadvertently erased.
- the read head sensor is positioned between two shields 22 . These shields 22 can also result in erasure at track positions that are relatively far from the track where the write head pole 21 is positioned.
- the write-around shield WAS
- Embodiments of the present invention address the problem of track erasure dependence on written data frequency and/or pattern.
- a timing circuit has been described in the prior art to address the problem of track erasure in a similar application, but in that case the peak current for a particular magnetic transition could only be adjusted depending on the previous bits (i.e., a look-back algorithm).
- this look-back strategy cannot be used to, for example, adjust the overshoot current of the first transition within a dibit or the first transition preceding a long magnet, both of which have historically been problematic.
- Embodiments of the invention include disk drives with a Channel System and Write Driver Preamp architecture that dynamically adjusts the write driver's signal wave-shape depending on the write data signal pattern.
- the wave-shape control signal is generated in the Channel and transmitted to the Write Driver Preamp.
- the wave-shape control signal can be transmitted to the Write Driver Preamp on a dedicated signal line, transmitted on the read signal lines or be encoded along with the write data and transmitted as a composite signal on the write lines.
- the wave-shape control signal can be encoded as an amplitude-level modulated (AML) signal that can be separately transmitted or can be combined with the Current-mode logic (CML) write data signal to form an AML-CML signal that is transmitted on the write data lines.
- the Write Driver Preamp demodulates the AML-CML to determine the required wave-shape for the write driver output signal.
- the Channel analyzes the bit patterns in the data to be written to determine the overshoot amplitude modulation. This system will be referred to as the Channel-Preamp Dynamic Wave Shape (CP-DWS) system.
- CP-DWS Channel-Preamp Dynamic Wave Shape
- Embodiments can implement a look-ahead, look-back, or combined look-back/look-ahead strategies.
- Embodiments of the invention provide discrete n-level overshoot amplitude control using amplitude-level modulated (AML) signal.
- One embodiment implements a look-ahead strategy overshoot amplitude control where the overshoot amplitude for each transition depends only on the subsequent (following) bits in the data stream and not on any previously recorded data.
- An embodiment of the Write Driver Preamp includes a delay path for the CML write data signal and an overshoot amplitude control unit that demodulates the AML signal, times the trigger and accesses the preset parameter values.
- pre-setting of the positive current overshoots (OSA:+Iw) and negative overshoots (OSA: ⁇ Iw) is not done in the same phase as the write data.
- This embodiment allows pre-loading of the overshoot amplitude control for the subsequent write data transition. Alternating switching buffer with separate Trigger Signal Generators for positive (+Iw) and negative write currents ( ⁇ Iw) are used, which allows a one time period (1T) setup time between transitions.
- a preprogrammed delay between the write data and the overshoot control signal is controlled by the Channel, which can be programmed to adjust this delay to accommodate the phase in the Channel and the Write Driver Preamp.
- FIG. 1 is a block illustration of selected components of a prior art disk drive.
- FIG. 2 illustrates the adjacent tracks erasure problem for repeatedly written tracks in the prior art.
- FIG. 3 is a block diagram illustrating selected components in a disk drive with a Channel-Preamp Dynamic Wave Shape system according to a first embodiment of the invention.
- FIG. 4A is a signal timing diagram showing selected signals for a sample data stream for an embodiment of the invention using look-ahead with 3-level overshoot control.
- FIG. 4B is a signal timing diagram showing selected signals for a sample data stream for an embodiment of the invention using look-ahead with 2-level overshoot control.
- FIG. 5 is a block diagram illustrating selected components in a disk drive with a Channel-Preamp Dynamic Wave Shape system according to a second embodiment of the invention.
- FIG. 6 is a block diagram illustrating selected components in a disk drive with a Channel-Preamp Dynamic Wave Shape system according to a third embodiment of the invention.
- FIG. 3 is a block diagram illustrating selected components in a disk drive with a Channel-Preamp Dynamic Wave Shape (CP-DWS) system according to a first embodiment of the invention.
- Components in the embodiment reside in the channel 31 A and in the write driver Preamp 18 A.
- the write data stream which is input into the channel 31 A, is initially processed by the WRITE DATA PROCESS BLOCK 36 to detect the data patterns for overshoot amplitude adjustment.
- BLOCK 36 generate the corresponding overshoot amplitude signal that drives the Amplitude-Level Modulation (AML MOD) UNIT 33 , which in turn drives the WRITE BUFFER 32 .
- the data stream output signal from WRITE BUFFER 32 which goes to the Write Driver Preamp 18 A, is a differential signal that includes amplitude modulation.
- the channel uses AML modulation to assign a predetermined specified overshoot to each bit sequence.
- the data patterns and the corresponding overshoot amplitudes can be determined empirically for a particular disk drive.
- the AML modulation can be a minimum of two levels to have two-amplitude-level modulation or even higher levels (three, four, etc.). The minimum two level would then be a simple two-level overshoot control.
- Write Driver Preamp 18 A generates the write driver output signal which is connected to the write coil in the slider.
- the output of the write driver's signal in the Preamp is controlled by the AML-CML signal 39 , where the CML portion of the signal controls the reversal signal for the coil at the output of the write driver, which determines the magnetic transitions, and the AML portion controls the overshoot.
- the channel output has an AML modulator to assign the specified overshoot amplitude to each bit sequence.
- the Write Driver Preamp 18 A has an AML Demodulator 41 (or peak threshold logic) for determining the overshoot settings.
- Latch Clock 45 is set by transitions in the data (T n ).
- the delays, OSA Preset Delay D 1 35 and Write Path Delay D 2 34 are set such that the Preset Buffer 42 is loaded in time for the subsequent transition, and delay D 3 allows for the trigger signal (Trg) 46 S from Trigger Sample Block 46 to capture the AML-CML signal for demodulation or peak detection.
- the AML DMOD block 41 converts the peak signal to the OSA level and supplies this signal to Trigger Sample Block 46 .
- the Latch Clock 45 signal triggers sampling of the OSA level in the Trigger Sample Block 46 for processing, 46 S by the write driver 51 , which sets the corresponding OSA output signal to the write head.
- FIG. 4A is a signal timing diagram for an embodiment of a Channel-Preamp Dynamic Wave Shape (CP-DWS) system using look-ahead with 3-level overshoot control.
- the timing diagram in FIG. 4A illustrates the timing relationships of the trigger signal (Trg) 46 S and other signals.
- the selected sample data bit values in the write data received by the channel 31 A are shown along the top.
- the system uses the write data transitions as the latch/trigger signal for capturing and loading the preset buffer.
- the AML-CML signal generated by the channel 31 A, and the resulting preamp write driver output with dynamic wave shaping, are shown.
- the AML-CML signal level (amplitude) at the beginning of each transition represents (encodes) the overshoot current that should be applied by the preamp.
- Other overshoot signal encodings are also possible in other examples/embodiments.
- three levels of overshoot are available, but in general N-levels can be used.
- the 1T-patterns are given additional overshoot current, while long magnets are written using reduced peak currents to minimize cross track interference/erasure.
- Empirical optimization of the pattern-dependent current settings will be required to achieve optimal error rates while at the same time reducing cross-track interference and maximizing areal density in a particular embodiment.
- the example embodiment illustrated here uses a look-ahead strategy, where the overshoot applied for each transition depends only on the following bits in the data stream and not on any previously recorded data.
- the general method can also be used to include look-back only and combined look-back/look-ahead strategies, to provide the greatest ability to tune the write waveform for each specific bit sequence in the data.
- the waveform example in FIG. 4A as described above is summarized in Table 1 below (for non-return-to-zero (NRZ) encoding), where the underlined data bit transition represents the target bit.
- TNEXT refers to number of time periods until the next transition, i.e. “looking ahead.”
- the 3-levels are referred to as low, nominal and high.
- the nominal value is selected when a number of time periods until a next magnetic transition for the set of data bits is in a predetermined range, which in this example includes two and three time periods (2T and 3T).
- the number of low-frequency (NLF) bits is three, so any transition followed by a magnet longer than three time period (3T) patterns will be written with a reduced (low) overshoot, while any one time period (1T) patterns will be written with increased (high) overshoot.
- 3T three time period
- 1T one time period
- This strategy will facilitate recording 1T patterns (using large peak currents) while at the same time reducing cross-track interference issues due to the long magnets by using lower peak currents.
- the embodiment described above is an integrated solution that utilizes the write-signal path to carry the overshoot control signal.
- Other alternative embodiments include multiplexing the read-signal line to transmit the overshoot signal level, because the read-signal line is not otherwise used during writing.
- Another alternative embodiment could use a dedicated signal line to transmit the overshoot signal level. Both of these alternatives would have the overshoot signal level synchronized with the write data signal that would be triggered/loaded by the write signal transitions.
- FIG. 5 shows a second embodiment with an alternative architecture, with Write Driver Preamp 18 B, OSA Preset Delay D 1 35 B and Write Path Delay D 2 34 B, where pre-setting of the positive current overshoots, OSA:+Iw, and negative overshoots, OSA: ⁇ Iw, is not done in the same phase as the write data.
- This architecture would allow pre-loading of the overshoot for the subsequent write data transition.
- the embodiment shown in FIG. 5 uses an alternating switching buffer 47 with separate Trigger Sample Blocks 47 P, 47 N for positive (+Iw) and negative write currents ( ⁇ Iw), which allows a 1T setup time between transitions. Note that this embodiment does not require a preset buffer.
- FIG. 6 shows a third embodiment of the invention that uses a separate signal path for the overshoot control.
- This embodiment uses channel 31 C which provides an overshoot control signal 33 S from Write Buffer 32 C, which is multiplexed on the read signal lines, which are not otherwise used during write operations.
- FIG. 4B is a signal timing diagram showing selected signals for a sample data stream for an embodiment of the invention using look-ahead with 2-level overshoot control.
- the 2-levels are referred to as nominal and high.
- the nominal value is selected when a number of time periods until a next magnetic transition for the set of data bits is greater than a predetermined value, which in this example is more than two time period (>2T). All other time periods, which in this example include only one and two time periods ( ⁇ 2T) patterns, will be written with increased (high) overshoot.
- FIG. 4B also shows a 1 ⁇ 2 T CML delay shift, which is controlled by the Channel 31 A. Although a 1 ⁇ 2 T is shown, the Channel can be programmed to adjust this delay to accommodate the phase in the Channel 31 A and the Write Driver Preamp 18 A.
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- Engineering & Computer Science (AREA)
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Abstract
Description
TABLE 1 |
Example with look-ahead with 3-level overshoot control. |
Example | ||||
Description | TNEXT | Data | (TNEXT) | OSA (total) |
Nominal OSA | 2T ≦ TNEXT ≦ | *101 | (=2T) | OSA |
NLFT | ||||
Low OSA for | >NLFT | *10 . . . 01 | (>3T) | OSA − OSALF |
long magnets | ||||
High OSA for | =1T | *11 | (=1T) | OSA + |
high freq. | OSADibit1 | |||
TABLE 2 |
Example with look-ahead with 2-level overshoot control. |
Example | |||
Description | TNEXT | Data | OSA (total) |
Nominal OSA | >2T | *10101010001 | OSA |
High OSA | ≦2T | *1110101011 | OSA + OSADibit1 |
Claims (18)
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/804,063 US9275656B1 (en) | 2015-07-20 | 2015-07-20 | Disk drive with channel and preamp with dynamic write-current control for write head |
GBGB1611844.0A GB201611844D0 (en) | 2015-07-20 | 2016-07-07 | Disk drive with channel and preamp with dynamic write-current control for write head |
DE102016008795.1A DE102016008795A1 (en) | 2015-07-20 | 2016-07-19 | Channel drive with channel and preamplifier with dynamic write current control for write head |
CN201610576043.3A CN106373597A (en) | 2015-07-20 | 2016-07-20 | Disk drive with channel and preamp with dynamic write-current control for write head |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/804,063 US9275656B1 (en) | 2015-07-20 | 2015-07-20 | Disk drive with channel and preamp with dynamic write-current control for write head |
Publications (1)
Publication Number | Publication Date |
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US9275656B1 true US9275656B1 (en) | 2016-03-01 |
Family
ID=55360035
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US14/804,063 Active US9275656B1 (en) | 2015-07-20 | 2015-07-20 | Disk drive with channel and preamp with dynamic write-current control for write head |
Country Status (4)
Country | Link |
---|---|
US (1) | US9275656B1 (en) |
CN (1) | CN106373597A (en) |
DE (1) | DE102016008795A1 (en) |
GB (1) | GB201611844D0 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9672864B2 (en) * | 2015-10-09 | 2017-06-06 | Seagate Technology Llc | Changing characteristics of signal patterns to reduce adjacent track interference |
US9779763B1 (en) | 2016-04-29 | 2017-10-03 | Seagate Technology Llc | Write signal adjustment |
US10991391B1 (en) | 2020-02-04 | 2021-04-27 | Headway Technologies, Inc. | Circuits and methods for modifying the write current waveform to improve track density in HDD |
US11031039B1 (en) | 2020-08-19 | 2021-06-08 | Headway Technologies, Inc. | Circuits and methods for optimizing write current waveform for main pole relaxation in perpendicular magnetic recording |
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WO2001029829A1 (en) | 1999-10-21 | 2001-04-26 | Sony Electronics Inc. | Architecture for a hard disk drive write amplifier circuit with programmable controls |
US6798591B2 (en) | 2001-10-29 | 2004-09-28 | Texas Instruments Incorporated | Reference circuit for write driver circuit with programmable write current, overshoot duration and overshoot amplitude control |
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US6870697B2 (en) | 2002-06-24 | 2005-03-22 | Hitachi, Ltd. | Overshoot current phase/amplitude control for hard disk drive write current |
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US7660064B2 (en) | 2004-10-28 | 2010-02-09 | Agere Systems Inc. | Methods and apparatus for controlling write driver current |
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US20130057319A1 (en) | 2011-09-06 | 2013-03-07 | Xin Liu | Method and circuit for precisely controlling amplitude of current-mode logic output driver for high-speed serial interface |
US8413020B2 (en) * | 2009-08-12 | 2013-04-02 | Lsi Corporation | Systems and methods for retimed virtual data processing |
US20130083419A1 (en) | 2011-09-30 | 2013-04-04 | David M. Springberg | Disk-based storage device having write signal compensation for magnetization polarity of adjacent bits |
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US8565047B2 (en) | 2011-04-28 | 2013-10-22 | Lsi Corporation | Systems and methods for data write loopback based timing control |
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JP2005078748A (en) * | 2003-09-02 | 2005-03-24 | Toshiba Corp | Disk storage device and recording current control method |
JP2007172751A (en) * | 2005-12-22 | 2007-07-05 | Hitachi Global Storage Technologies Netherlands Bv | Disk apparatus and control method of disk apparatus |
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US8792197B1 (en) * | 2013-09-20 | 2014-07-29 | Lsi Corporation | Storage device with driver controller providing pattern-dependent write functionality |
-
2015
- 2015-07-20 US US14/804,063 patent/US9275656B1/en active Active
-
2016
- 2016-07-07 GB GBGB1611844.0A patent/GB201611844D0/en not_active Ceased
- 2016-07-19 DE DE102016008795.1A patent/DE102016008795A1/en active Pending
- 2016-07-20 CN CN201610576043.3A patent/CN106373597A/en active Pending
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WO2001029829A1 (en) | 1999-10-21 | 2001-04-26 | Sony Electronics Inc. | Architecture for a hard disk drive write amplifier circuit with programmable controls |
US6798591B2 (en) | 2001-10-29 | 2004-09-28 | Texas Instruments Incorporated | Reference circuit for write driver circuit with programmable write current, overshoot duration and overshoot amplitude control |
US6826003B1 (en) | 2002-01-31 | 2004-11-30 | Western Digital Technologies, Inc. | Disk drive comprising a pattern dependent overshoot circuit for controlling write current overshoot |
US6870697B2 (en) | 2002-06-24 | 2005-03-22 | Hitachi, Ltd. | Overshoot current phase/amplitude control for hard disk drive write current |
US7839589B2 (en) | 2004-03-22 | 2010-11-23 | Texas Instruments Incorporated | Write current waveform asymmetry compensation |
US7660064B2 (en) | 2004-10-28 | 2010-02-09 | Agere Systems Inc. | Methods and apparatus for controlling write driver current |
US7450326B2 (en) | 2005-03-31 | 2008-11-11 | Matsushita Electric Industrial Co., Ltd. | Method to determine temperature dependent write pre-compensation in a hard disk drive |
US7830631B2 (en) | 2006-08-04 | 2010-11-09 | Hitachi Global Storage Technologies Netherlands B.V. | Controlling an overshoot amplitude level based on a recording data pattern in a magnetic disk drive |
US8413020B2 (en) * | 2009-08-12 | 2013-04-02 | Lsi Corporation | Systems and methods for retimed virtual data processing |
US8565047B2 (en) | 2011-04-28 | 2013-10-22 | Lsi Corporation | Systems and methods for data write loopback based timing control |
US20130057319A1 (en) | 2011-09-06 | 2013-03-07 | Xin Liu | Method and circuit for precisely controlling amplitude of current-mode logic output driver for high-speed serial interface |
US20130083419A1 (en) | 2011-09-30 | 2013-04-04 | David M. Springberg | Disk-based storage device having write signal compensation for magnetization polarity of adjacent bits |
US20130128375A1 (en) | 2011-11-22 | 2013-05-23 | Lsi Corporation | Magnetic Recording System With Multi-Level Write Current |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9672864B2 (en) * | 2015-10-09 | 2017-06-06 | Seagate Technology Llc | Changing characteristics of signal patterns to reduce adjacent track interference |
US9779763B1 (en) | 2016-04-29 | 2017-10-03 | Seagate Technology Llc | Write signal adjustment |
US10991391B1 (en) | 2020-02-04 | 2021-04-27 | Headway Technologies, Inc. | Circuits and methods for modifying the write current waveform to improve track density in HDD |
US11031039B1 (en) | 2020-08-19 | 2021-06-08 | Headway Technologies, Inc. | Circuits and methods for optimizing write current waveform for main pole relaxation in perpendicular magnetic recording |
Also Published As
Publication number | Publication date |
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DE102016008795A1 (en) | 2017-01-26 |
GB201611844D0 (en) | 2016-08-24 |
CN106373597A (en) | 2017-02-01 |
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